This project will examine responses of the treehold mosquito, Aedes triseriatus, to variation in local climatic conditions, with a particular focus on precipitation patterns and the evolution of variable dormancy prior to egg hatch. The central hypothesis of the project is that relative dry habitats should have a higher probability of desiccation, which should promote the evolution of greater variation in delays before hatching. Questions associated with this issue concern the association of other aspects of individual fitness (e.g. larval development rate, adult body size, sensitivity to crowding) with hatch delay, as well as the relationship between the variability in hatch rate for a population and the tendency of eggs to be inhibited from hatching by high densities of larvae. The central questions will be addressed by comparing hatch rates for 23 populations from New Jersey to North Carolina. All of these populations have experienced comparable temperature regimes during the last three decades, but they vary by as much as a factor of two in annual precipitation. Of these, two populations with the most variable hatch times and two with the least variable and earliest hatching will be examined to assess the degree of association with other features influencing fitness. We hypothesize that hatch time variation has been most important in the most dissection-prone environments, and that other fitness-related traits will be most heavily structured around hatch delay in those populations. We will also compare the sensitivity of eggs from these four populations to the presence of larvae, anticipating that the populations with the lowest levels of hatch time variation should exhibit the largest degree of egg sensitivity. If differences in egg hatching strategies can be found in the laboratory, a test for the importance of climate will be performed by comparing the success of experimental cohorts from the two most different populations, as well as hybrid cohorts, in simulated habitats placed in field conditions